The present invention is directed to a method and apparatus for manufacturing a refrigeration system including a compressor externally mounted on a heat exchanger shell. The present invention is described in terms of a chiller system but is intended to be generally applicable to all refrigeration and air conditioning systems.
Chillers are refrigeration systems which provide a flow of chilled water for cooling large building complexes, campuses or the like. The chiller comprises a compressor, a condenser, an expansion device and an evaporator, all serially linked in a closed circuit. These chiller components are also physically arranged to take advantage of gravity during the operation of the chiller system. Condensed refrigerant flows downhill from the condenser through the expansion device to the evaporator where the refrigerant vaporizes in absorbing heat. The vaporized refrigerant is drawn up by compressor suction through a suction pipe and elbow section into the compressor where that refrigerant is pressurized. The pressure moves the pressurized refrigerant from the compressor through a discharge pipe and elbow section to the condenser where the refrigerant is condensed into a liquid and the cycle commences anew.
The layout of a typical chiller system is such that the compressor is located above the evaporator, and the condenser is laterally displaced between the compressor and evaporator. This is similar to a tri-level house where the condenser is located at the level of the main floor with the compressor half a flight up and mounted above the evaporator, and the evaporator located half a flight down from the condenser.
The compressor is a large heavy object and must be stable to support its high speed operation. A direct drive compressor has a normal speed of operation of about 3600 RPM, and a gear drive compressor has a normal speed of operation ranging between 10,000 and 12,000 RPM. In either case, the compressor must be firmly mounted to the evaporator shell so that the high speed rotation of the compressor and its motor, and the weight of that compressor and motor have stable operation. There are various ways and devices to assemble such a compressor to meet these requirements.
In assembling a chiller system, the previous chiller systems position the compressor motor above the evaporator shell, attach the compressor motor to the shell using a mounting plate, and then custom fit the discharge and suction pipe and elbow sections to the resultant compressor location. The fitting of the discharge and suction pipe and elbow sections is a time consuming, laborious process which is occurring on the final assembly line and thus delaying production. Furthermore, standardized discharge and suction pipe and elbow sections cannot be used because the heat exchanger shell upon which the compressor is mounted is inherently unique due to variations resulting from the manufacturing process. The shells are formed of rolled steel and have minor individual variations from the rolling process. More critically, the shells are welded into a cylinder using a lateral weld along the entire length of the shell. The lateral weld causes distortion, distorting each shell uniquely and unpredictably.
Traditionally, the compressor is mounted to the shell and the adjustments are made in the discharge and suction pipe and elbow sections of the compressor. To improve the manufacturing process, it is desirous to standardize the suction and diffuser pipe and elbow sections. It is also desirous to manufacture the suction and discharge pipe and elbow sections at a side location rather than on the final assembly line.